Hi Marita Lawson. This is a great question! During a cardio workout you will burn more calories. After a weight-training workout, metabolism can be boosted for up to 38 hours post-workout, meaning that you'll be burning more calories doing your normal activities. In short, if you can do both, that is ideal. And ideally, you will want to do the strength training session first, followed by the cardio session. Your heart rate is higher during your cardio bout and that means more calories burned.